1. Technical Field
The present invention relates to double-gate FETs (Field Effect Transistors), and more specifically, to double-gate FETs whose double gates are electrically disconnected from each other.
2. Related Art
Dopant fluctuations are becoming a serious problem in Vt (threshold voltage) control in advanced semiconductor devices. As semiconductor devices become smaller and smaller in size, Vt control becomes more difficult. A known solution is to use back gates (in addition to front gates) in the semiconductor devices to control Vt. Without precise alignment between the top and bottom gates, however, the performance advantage of dual gates is decreased or lost completely.
As a result, there is always a need for new methods for forming transistors with aligned double gates. The present invention provides such a new method.